Apparatus for measuring spectra

Abstract

Apparatus for measuring spectra from one or more samples, the apparatus including a reference waveguide that receives illuminating radiation used to illuminate at least one sample, at least one sample waveguide that receives sample radiation at least one of reflected from and transmitted through a respective sample, an optical system that spatially distributes radiation from each of the waveguides based on a frequency of the radiation, and focuses radiation from the optical fibres into an imaging plane and an imaging device that captures an image of the focused and spatially distributed radiation from the imaging plane so that the image includes respective spectra from each of the waveguides.

The claims defining the invention are as follows: 
     
       1. Apparatus for measuring spectra from one or more samples, the apparatus including:
 a) a reference waveguide that receives illuminating radiation used to illuminate at least one sample, wherein the illuminating radiation is at least one of:
 i) natural light; 
 ii) solar radiation; and, 
 iii) a non-artificial source of illumination; 
 
 b) at least one sample waveguide that receives sample radiation at least one of reflected from and transmitted through a respective sample; 
 c) an optical system that:
 i) spatially distributes radiation from each of the waveguides based on a frequency of the radiation; and, 
 ii) focuses radiation from the optical fibres into an imaging plane; and, 
 
 d) an imaging device including a sensor that captures an image of the focused and spatially distributed radiation from the imaging plane so that the image includes respective spectra from each of the waveguides. 
 
     
     
       2. Apparatus according to  claim 1 , wherein the optical system:
 a) spatially distributes radiation from each waveguide in a first direction based on the frequency of the radiation; and, 
 b) focuses radiation from the waveguides so that the radiation from each fibre is spaced in a second direction perpendicular to the first direction. 
 
     
     
       3. Apparatus according to  claim 1 , wherein at least one of:
 a) the waveguides are optical fibres; 
 b) the optical system includes a slit and collimating lens and wherein output ends of the waveguides direct radiation through the slit and collimating lens 
 c) the optical system includes:
 i) diffraction grating that spatially distributes radiation; and, 
 ii) one or more lenses that focus the spatially distributed radiation; 
 
 d) the imaging device includes at least one of:
 i) a CMOS; 
 ii) an infrared sensor; 
 iii) a single pixel sensor; and, 
 iv) a CCD sensor 
 
 e) the apparatus includes a diffusion member at an input to the reference waveguide. 
 
     
     
       4. Apparatus according to  claim 1 , wherein an input end of the sample fibres includes at least one of:
 a) an input lens for focusing radiation from the sample; 
 b) an input lens having at least one of:
 i) a focal length of at least one of:
 (1) 1 cm to 100 cm; 
 (2) 5 cm to 50 cm; and, 
 (3) 10 cm to 30 cm; and, 
 
 ii) a field of view of at least one of
 (1) 1 cm2 to 10 cm2; and, 
 (2) 2 cm2 to 5 cm2; and, 
 
 
 c) a polariser for selectively filtering radiation from the sample. 
 
     
     
       5. Apparatus according to  claim 1 , wherein the apparatus includes at least one of:
 a) a second reference fibre that receives reference radiation from at least one of:
 i) a reference target; 
 ii) a reference sample; and, 
 iii) a reference illumination source; and, 
 
 b) a reference illumination source adapted to generate illumination including particular frequencies of radiation. 
 
     
     
       6. Apparatus according to  claim 1 , wherein the apparatus includes a support for supporting input ends of at least some of the waveguides and wherein at least one of:
 a) the input ends of at least some of the waveguides are movably mounted to the support, thereby allowing a relative field of view of the waveguide to be adjusted; and, 
 b) wherein the support includes a boom, and wherein at least some of the sample waveguide inputs are spaced along the boom allowing reflected radiation to be received from a number of spatially distributed samples simultaneously. 
 
     
     
       7. Apparatus according to  claim 6 , wherein the boom at least one of:
 a) is coupled to a handle allowing a user to carry the boom, and thereby manually position the waveguides relative to one or more samples; and, 
 b) extends laterally from a vehicle. 
 
     
     
       8. Apparatus according to  claim 1 , wherein the apparatus is adapted for measuring spectra from a water body and includes at least one of:
 a) a pair of waveguides including:
 i) a reference waveguide arranged to capture downwelling light through a diffuser; and, 
 ii) a sample waveguide capturing light reflected from the water body; and, 
 
 b) a pair of waveguides including:
 i) a sample waveguide provided at an angle orientated downwardly to capture light reflected from the water body; and, 
 ii) a reference waveguide provided at a corresponding angle orientated upwardly to capture light from a part of the sky that is directly reflected from the water body onto the sample waveguide. 
 
 
     
     
       9. Apparatus according to  claim 1 , wherein at least one of:
 a) the sensor is aligned with the imaging plane; 
 b) the sensor receives radiation from at least one reflector aligned with the imaging plane; 
 c) the apparatus includes a modulator for selectively transferring radiation from the imaging plane to the imaging device; and, 
 d) the apparatus includes a modulator including at least one of a linear digital mirror device and a liquid crystal on silicon device. 
 
     
     
       10. Apparatus according to  claim 1 , wherein the apparatus includes at least one processing device that includes a processor or other logic implementation and that:
 a) receives image data from the imaging device; and, 
 b) generates spectral data by:
 i) identifying one or more rows of pixels within the image data, the one or more rows of pixels being indicative of radiation from the waveguides; and, 
 ii) selectively encoding the one or more rows of pixels to form the spectral data; 
 
 c) at least one of:
 i) stores spectral data based on the received image data; 
 ii) stores spectral data together with reference data collected from one or more sensors; and, 
 iii) transmits spectral data based on the received image data. 
 
 
     
     
       11. Apparatus according to  claim 10 , wherein the at least one processing device generates spectral data by:
 a) identifying one or more second order pixels within the image data based on a pixel location within the image; and, 
 b) selectively encoding channels associated with the one or more second order pixels to form the spectral data, wherein the at least one processing device selectively encodes the second order pixels using at least one of
 i) a red channel in which red pixels are at least partially sensitive to infrared light; 
 ii) a red and a green channel in which red and green pixels are at least partially sensitive to infrared light; 
 iii) an infrared channel; and, 
 iv) signals from a red Bayer filter channel for radiation wavelengths from 650 nm to 1000 nm. 
 
 
     
     
       12. Apparatus according to  claim 10 , wherein the at least one processing device:
 a) generates the spectral data by performing principle component analysis on the received image data to determine principle component coefficients; and, 
 b) transmits spectral data in the form of the principle component coefficients and wherein the at least one processing device is populated with principle components based on the nature of the sample to be analysed. 
 
     
     
       13. Apparatus according to  claim 1 , wherein the apparatus includes at least one processing device that includes a processor or other logic implementation and that receives image data from the imaging device and at least one of:
 a) determines a sample spectra for each sample by determining a ratio of the sample radiation and the illuminating radiation; and, 
 b) performs a wavelength calibration of the sample spectra by at least one of:
 i) identifying a known combination of frequencies in the illuminating radiation; 
 ii) identifying a known frequency in a reference spectra measured from a reference sample; and, 
 iii) identifying a known frequency in illuminating radiation from a reference illuminating source. 
 
 
     
     
       14. Apparatus according to  claim 1 , wherein the apparatus includes at least one processing device that includes a processor or other logic implementation and that:
 a) receives image data from the imaging device; 
 b) determines a background spectra from the spectral data, wherein the background spectra is determined by identifying background pixels based on a defined location in the image data; and, 
 c) uses the background spectra to determine the sample spectra. 
 
     
     
       15. Apparatus according to  claim 1 , wherein
 the reference waveguide has an input directed at least one of:
 a) upwardly; 
 b) skywards; 
 c) towards a natural illumination source; and, 
 d) towards a non-artificial illumination source. 
 
 
     
     
       16. Apparatus according to  claim 1 , wherein the apparatus includes at least one processing device that includes a processor or other logic implementation and that processes the sample radiation to compensate for sources of errors, wherein the sources of errors include at least one of:
 a) exposure variability; 
 b) sensor noise; 
 c) sensor wavelength drift; 
 d) sensor sensitivity drift; 
 e) time dependent drift; 
 f) temperature dependent drift; and, 
 g) changes in illuminating radiation. 
 
     
     
       17. Apparatus according to  claim 1 , wherein the apparatus uses an imaging device having at least one of:
 a) a temperature response coefficient selected from the group including:
 i) greater than ±0.1% per ° C.; 
 ii) greater than ±0.5% per ° C.; and, 
 iii) greater than ±1% per ° C.; 
 
 b) a maximum drift in background current over the range 0° C. to 80° C. selected from the group including:
 i) greater than 10%; 
 ii) greater than 50%; 
 iii) greater than 200%; and, 
 iv) greater than 500%; 
 
 c) a maximum drift in measurement sensitivity over the range 0° C. to 80° C. selected from the group including:
 i) less than 20%; and, 
 ii) less than 10%; 
 
 d) a wavelength drift over the range 0° C. to 80° C., over a period of 1 year, selected from the group including:
 i) greater than 3 nm; 
 ii) greater than 5 nm; 
 iii) greater than 10 nm; and, 
 iv) up to 50 nm; 
 
 e) a linearity over the range 0° C. to 80° C. selected from the group including:
 i) greater than 1%; 
 ii) greater than 2%; and, 
 iii) greater than 5%; and, 
 
 f) a signal to noise ratio selected from the group including:
 i) less than 2000:1; 
 ii) less than 1000:1; 
 iii) less than 500:1; and, 
 iv) less than 100:1. 
 
 
     
     
       18. Apparatus according to  claim 1 , wherein the apparatus senses radiation in at least one of:
 a) 350 nm-1000 nm; 
 b) 350 nm-750 nm; 
 c) 350 nm-650 nm; 
 d) 400 nm-700 nm; 
 e) 650 nm-1000 nm; 
 f)10 nm-380 nm; 
 g) 750 nm-1400 nm; and, 
 h) 1400 nm-5500 nm. 
 
     
     
       19. Apparatus according to  claim 1 , wherein the apparatus is configured for use in at least one of:
 a) water quality monitoring: 
 b) agriculture monitoring; 
 c) environmental monitoring; 
 d) food monitoring; 
 e) pharmaceutical monitoring; 
 f) geological monitoring; and, 
 g) mine monitoring. 
 
     
     
       20. A method of measuring spectra from one or more samples, the method including:
 a) using a reference waveguide to receive illuminating radiation used to illuminate at least one sample, wherein the illuminating radiation is at least one of:
 i) natural light; 
 ii) solar radiation; and, 
 iii) a non-artificial source of illumination; 
 
 b) using at least one sample waveguide to receive sample radiation at least one of reflected from and transmitted through a respective sample; 
 c) using an optical system to:
 i) spatially distribute radiation from each of the waveguides based on a frequency of the radiation; and, 
 ii) focus radiation from the optical fibres into an imaging plane; and, 
 
 d) using an imaging device including a sensor to capture an image of the focused and spatially distributed radiation from the imaging plane so that the image includes respective spectra from each of the waveguides.